SEAT Ibiza - rwd turbo
Discussion
Fastdruid said:
Max_Torque said:
Due to space constraints with the tight engine packaging, i use a TRW Electrohydraulic PAS pump, "borrowed" from a Ford Focus ST. This runs into my GrpA Cossie steering rack (only 1.2 turns Lock to Lock).
The TRW pump takes vehicle and engine speed and handwheel rate over CAN, and changes it's pump speed to suit, and although i have had this working, i've never been happy with the way it responds in my car, with a steering system quite different from the original ST.
I know someone at TRW who works on EHPAS if you have any other queries on it I could ask, although no promises as some stuff he may not be allowed to answer. The TRW pump takes vehicle and engine speed and handwheel rate over CAN, and changes it's pump speed to suit, and although i have had this working, i've never been happy with the way it responds in my car, with a steering system quite different from the original ST.
Pretty much the only think i don't know is the CAN protocol to reflash/code the pump module to change it's internal characteristic maps. However, as i use my chassis dynamics module to drive the unit (send it commands over CAN) i can effectively modify the units response by sending it modified data. ie, if i want more assistance vs vehicle speed, i just send it a lower than true vehicle speed and vise versa ;-)
Ok, every car, no matter how well designed & built has gotta have a bodge somewhere. Well, here's mine:
Yup^^^ that horrible mess of brackets and mounts is the cough, MOT, cough mechanical handbrake system. Mounted on the differential input shaft it's a brembo mech handbrake caliper clamping a custom "disc". I've not decided what i'm going to actuate it with yet, either just a std lever mounted on the sill side of the drivers seat but possibly with an electronic actuator to avoid having to sort out the cable run into the cabin etc.
Luckily, you can't see it normally as it's hidden between diff and gearbox:
(there's a proper "flyoff" hydraulic handbrake to use for turning round duties....... ;-)
Yup^^^ that horrible mess of brackets and mounts is the cough, MOT, cough mechanical handbrake system. Mounted on the differential input shaft it's a brembo mech handbrake caliper clamping a custom "disc". I've not decided what i'm going to actuate it with yet, either just a std lever mounted on the sill side of the drivers seat but possibly with an electronic actuator to avoid having to sort out the cable run into the cabin etc.
Luckily, you can't see it normally as it's hidden between diff and gearbox:
(there's a proper "flyoff" hydraulic handbrake to use for turning round duties....... ;-)
PhillipM said:
Max_Torque said:
I'll put kettle on while you lot get started then....... ;-)
Congratulations, you just volunteered to be official Tea b
h™ of the ensemble.
Currently there is a E46 M3 diff across the back axle. It's the GKN preloaded speed proportional item (has a light no slip preload and then applies cross axle locking in proportion to cross axle speed difference) and is entirely mechanical (uses internal oil pump driven by difference in speed between output shafts to apply pressure to a clutch pack across the diff.
This is a good diff as it is very "driveable" because the locking force is nice and linearly applied with slip. But it does mean you end up with a lot of cross axle speed difference and so it isn't as "tight" as say a conventional heavily preloaded plate type diff etc.
Ultimately, i'm going to use my prototype ABS system to attempt to add "Brake steer" to the diff at some point, although i'm not sure if i will have to take the existing plates/pump out to get that to work. I think not because the std locking gain is quite low. Another option is to fit the later "active" type internals to the diff, as used in the current M5 (and Jag XFR) that adds an external 'lecy oil pump to modify the cross axle locking ratio.
This is a good diff as it is very "driveable" because the locking force is nice and linearly applied with slip. But it does mean you end up with a lot of cross axle speed difference and so it isn't as "tight" as say a conventional heavily preloaded plate type diff etc.
Ultimately, i'm going to use my prototype ABS system to attempt to add "Brake steer" to the diff at some point, although i'm not sure if i will have to take the existing plates/pump out to get that to work. I think not because the std locking gain is quite low. Another option is to fit the later "active" type internals to the diff, as used in the current M5 (and Jag XFR) that adds an external 'lecy oil pump to modify the cross axle locking ratio.
rhinochopig said:
Interesting. Two glasses of wine in so stuggling to envisage how active braking would work on an E46 diff. Isn't the delta S between the two wheels what drives the pump and thus the clutch pack - reduce the delta and you reduce oil pressure.
As an Evo owner do mount the 'external' oil pump within the car. Or at least environmentally seal it better than Mitsubishi ever did
The answer is, It depends! Not much of an answer i know, but the reason i've added the cross axle speed sensors so i can log the actual speed differential of the "M" diff.As an Evo owner do mount the 'external' oil pump within the car. Or at least environmentally seal it better than Mitsubishi ever did
To act as an LSD, a system that applies the rear brakes must prevent the (more lightly loaded) inside wheel from overspeeding excessively, but if the system has enough control authority, it can underspeed that wheel, and add a positive yaw moment. Because of the tyre slip characteristic, fairly significant yaw moment can be created with as little as 15% slip. The question i don't know, is how does "15% slip" relate to what the M diff is setup to do. My suspicion, having driven a few M3s is that the diff is actually pretty loose, and doesn't really start to work until there is a large cross axle speed difference (ultimately, the M3 is a road car, not a track car, and so the diff is set up to be pretty benign)
On a 'wing and a prayer' part 2!
I've been having another stab at making some rear wing end plates / mounts that don't look totally gash ;-) tbh, it's a job i've been putting off as it a real PITA to do nicely. I've mocked up some end plates in MDF to get an idea how they look:
Not totally hideous, but hardly lovely either ;-(
It seems its really rather difficult to get a big wing on the back of a steep "hatchback" shaped car without that wing looking like it's fallen off a passing jumbo and just been nailed on where it fell....... Hmmm, think this needs a few more days looking at / rumination ......
I've been having another stab at making some rear wing end plates / mounts that don't look totally gash ;-) tbh, it's a job i've been putting off as it a real PITA to do nicely. I've mocked up some end plates in MDF to get an idea how they look:
Not totally hideous, but hardly lovely either ;-(
It seems its really rather difficult to get a big wing on the back of a steep "hatchback" shaped car without that wing looking like it's fallen off a passing jumbo and just been nailed on where it fell....... Hmmm, think this needs a few more days looking at / rumination ......
I used foam sheeting for quite a few of the more complex multi-curved carbon parts, like the roof scoop and dash inserts! These MDF plates are just a mock up to try to get an idea of what looks "nice" in terms of shape, bulk, and form on the back of the car. Without putting the whole car into CAD, it's the closest and quickest technique i've found to do that.
As you say, they will need to have more "form" added so they look less slabby, but don't worry, i have a plan for that..... ;-)
As you say, they will need to have more "form" added so they look less slabby, but don't worry, i have a plan for that..... ;-)
Podie said:
Max_Torque said:
CamMoreRon said:
Crikey that wing is a bit steep, isn't it? What is it from?
Co-incidentally, this happened today:
Prodrive HQ gets demolished
Ok, some jobs, like the rear wing are difficult ones, then occasionally, just occasionally, a nice easy one comes along!
Who'd have thought that the mounting bolt spacing on a Skoda Octavia handbrake lever is the exact same spacing as the side mounts of some Sparco race seats?
So, fitting "MOT" handbrake level literally took 1 min ;-)
Wish more jobs were that easy
Who'd have thought that the mounting bolt spacing on a Skoda Octavia handbrake lever is the exact same spacing as the side mounts of some Sparco race seats?
So, fitting "MOT" handbrake level literally took 1 min ;-)
Wish more jobs were that easy
gary71 said:
Nope Banbury!! After quite a few years Prodrive is moving a little bit down the road, still next to the M40, but to a site where they can amalgamate all their resources (excepts the MK composites dept) into one place.Fans of wonderful "bodges" will love this one:
^^^^^ That's a right royal fudge, to get a digital "crank position signal" out of my Motec M8 ecu! The device uses an LM2903N analogue comparitor as a basic "zero crossing" detector for the VR sensor that feeds in crankshaft position information. Unfortunately, there is no way of getting this data back out of the ecu, so i have fudged in an output line driver that is switched by the output of the existing comparitor. That digital data is then used by my new Knock sensing ecu, that needs accurate crank shaft position to correctly window the knock sensor signal integration. Luckily there was a spare pin on the main IO connnector of the ecu, which happened to be a 5v out, usually used to power sensors etc. So, by simply inserting a push/pull driver, soldered directly to the connector pin, i now have the necessary output ;-) Looks terrible, works nicely.......
^^^^^ That's a right royal fudge, to get a digital "crank position signal" out of my Motec M8 ecu! The device uses an LM2903N analogue comparitor as a basic "zero crossing" detector for the VR sensor that feeds in crankshaft position information. Unfortunately, there is no way of getting this data back out of the ecu, so i have fudged in an output line driver that is switched by the output of the existing comparitor. That digital data is then used by my new Knock sensing ecu, that needs accurate crank shaft position to correctly window the knock sensor signal integration. Luckily there was a spare pin on the main IO connnector of the ecu, which happened to be a 5v out, usually used to power sensors etc. So, by simply inserting a push/pull driver, soldered directly to the connector pin, i now have the necessary output ;-) Looks terrible, works nicely.......
The M8 is a pretty simple old ecu, and is mostly through hole components, so easy to track signal lines across the pcb. I don't have a schematic, but a quick look around the IC's failed to show any specific VR amplifier (LM1815 etc) so it pretty much had to use a comparitor or schmitt trigger. And, right next to the main processor was a dual channel analogue comparitor, so a quick probe with a scope popped up the requisite data lines straight away!
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